As a mobile terminal such as a cellular phone is recognized as a necessity of a daily life, various personal information has been stored in the mobile terminal. Particularly, as a memory storage capacity of a mobile terminal increases, and functions such as a mobile banking, a mobile stock transaction, etc. are added, personal information such as credit card information, stock transaction information, etc. which need security even more is stored in the mobile terminal. Therefore, recently, various methods for security of personal information stored in a mobile terminal are developed, and one of them is a method for executing a screen lock function when a user does not use a mobile terminal for a set time, and limiting an access of other people. When the screen lock function is executed, other additional functions except a basic function (for example, phone call reception function) of the mobile terminal may be blocked.
To unlock the screen lock of a mobile terminal that has executed a screen lock function, a user may input the same password as a password set in advance via an input key or form the same touch pattern as a touch pattern set in advance on the screen of a touchscreen.
Recently, various screen unlock methods capable of reinforcing security of personal information stored in the mobile terminal while allowing a user to use the mobile terminal more intuitively and conveniently are being studied.